It is generally recognized that combustion ability of certain heavy waste oil employed as furnace fuel may be improved by significantly pre-heating, vaporizing or pre-mixing such fuel with vaporized gases or other vapors prior to combustion. It is also understood, that in many cases a heating appliance itself does not provide sufficient heat to effect such fuel vaporization or similar fuel conditioning treatment, and therefore additional means, such as electric heating coils and the like, have to be installed in order to facilitate such conditioning or pre-combustion treatment of heavy waste oil fuels.
It is further known that such high temperature pre-heating and vaporizing treatment is especially useful to effectively reduce viscosity of such heavy fuel in order to render it at all usable, and a number of prior art disclosures describe various complicated methods and devices specifically developed for that purpose.
In U.S. Pat. No. 3,876,363, La Haye et al. discloses a method, which uses an external source of heat as well as part of the combustion chamber heat, to finely atomize a hydrocarbon fluid such as fuel oil to produce an emulsion of the oil with a secondary fluid prior to fuel oil combustion, thereby increasing combustion efficiency and minimizing pollutant discharge during combustion of such emulsified fuel mixture. For this purpose, the fuel is pre-heated to a temperature of between 150 to 250 degrees Fahrenheit.
In U.S. Pat. No. 2,840,148, I. W. Akesson discloses a furnace burner-blower arrangement, which employs pressure and heat to pre-treat heavy fuel oil prior to combustion. The fuel oil is heated by way of a heating element which is controlled by thermostats to maintain a certain oil temperature range, but without stating any specific and most advantageous operating fuel oil temperature range.
In U.S. Pat. No. 2,781,087, Peter Storti et al. disclose a rotary cup type, heavy oil burner system, which circulates the fuel through the burner on its way to the atomizer nozzle. This application further utilizes an electric heating device to pre-heat the fuel oil in a thermostatically controlled oil reservoir prior to combustion. This system presents a distinct improvement over other prior art, in that it greatly reduces the fuel oil temperature fluctuations inherent in other fuel pre-heating systems. However, no specific fuel oil operating temperature range is indicated to claim combustion efficiency or emission reduction.
In CA Patent No. 380,126, Andrew Palko discloses an oil burner comprising an electric heating element to pre-heat the burner so as to cause instant vaporization of the fuel oil as it is fed to the burner. This system includes temperature control means to regulate the fuel oil temperature without specifying any particular fuel oil temperature or temperature range, which would be required to obtain the claimed vaporization and desired combustion efficiency or emission reduction. In CA Patent No. 457,123, Earl J. Senninger discloses an oil burner especially adapted for heavy oils. Such heavy fuel oils are pre-heated by way of an electric heating element prior to reaching the atomizing nozzle of the burner unit. Here the desired fuel oil operating temperature range is described as a temperature to be such as to insure against carbonizing of the fuel, which would normally be a temperature just short of combustion.
In U.S. Pat. No. 4,392,820, Niederholtmeier discloses a system for operating a heating appliance comprising the combination of unheated conventional fuel oil and pre-heated heavy waste oil in two separate pressure controlled distribution networks, precluding any intermingling of the two fuel sources. The waste oil is pre-heated to it's flash point level in order to reduce its viscosity and to render it combustible, and is fed to the burner after conditioning the burner by first operating it for a period of time with conventional untreated fuel oil, facilitating subsequent combustion of treated waste oil.
For the purpose of pre-combustion treatment of natural gas and propane gas, as well as other conventional hydrocarbon fuels for use in appliances incorporating a burner located in a combustion zone, so as to increase the thermal efficiency of such fuels in accordance with the present invention, a different set of circumstances is required.
In order to effect thermal energy and combustion efficiency, and a noticeable reduction in harmful flue gas emission, an appliance burner will respond to fuel delivered to its burner nozzle at a constant and specifically elevated pre-combustion temperature level. Such elevated temperature must not be as high as to approach the flash point temperature of the fuel or as to begin vaporizing the fuel prior to combustion, as this would interfere with the function of the burner nozzle, resulting in a loss of thermal efficiency, and as such would be contrary to the teaching in this disclosure. In fact, the most advantageous fuel pre-combustion operating temperature, according to the present invention, is a moderate temperature range somewhat above a normally low fuel delivery temperature experienced during the heating season, but sufficiently high to effect fuel expansion and effecting fuel BTU input of the normally low temperature delivered fuel without causing interference with the conventional combustion process of the appliance.
During more frigid periods of the year, when heating appliances are usually in operation, fuel stored in storage tanks especially, and fuel transported in conduits exposed to the elements for considerable distances, remains at a temperature well below the optimal contemplated operating range, and pre-heating fuel economically could provide a number of significant advantages available for both gas and oil applications. Even appliances operating during the summer period, such as gas fired cooling appliances or residential, commercial and industrial water and process heaters, may operate more efficiently with the contemplated fuel treatment method and device.
It is an established fact that some fluid hydrocarbon fuels may expand in volume by approximately 15% when heated from 35 degrees to 115 degrees Fahrenheit. Therefore, in a situation where such fuel is delivered to the burner mechanism at a low temperature, especially when reaching levels below 35 degrees Fahrenheit, fuel pre-heating would automatically result in a possible expansion of fuel volume of up to 15% and more.
Furthermore, such pre-heated fuel delivered to the burner nozzle at its more optimal operating temperature would produce significantly more intense and complete combustion, as the expansion of fuel allows for a better fuel to air/oxygen ratio mix, resulting in a measurable increase in burner efficiency as well as a measurable decrease in harmful flue gas emission. It is estimated that burner efficiency could improve by up to 10%, while harmful flue gas emission could be reduced by up to 35%.
It therefore stands to reason that a simple device, which could provide an economical method for a moderate pre-heating of combustion appliance fuel, such as natural gas, propane gas or other conventional fluid hydrocarbon appliance fuel prior to combustion, would be most desirable.
All prior art examined however seems to be specifically designed to treat only unconventional combustion fuels like heavy fuel oils or waste oils, and then at much higher temperatures, up to the flash point level or up to the vaporization level, rather than moderately pre-heating a conventional combustion fuels such as gas or No. 2 fuel oil, and in all cases, such prior art must rely without exception on additional heating elements to effect the relatively high temperature pre-heating process to the level of up to or above fuel vaporization or up to the flash point level of the fuel. This is of course contrary to the teaching disclosed in the present invention and outside the function of the method and device contemplated and described further herein, and there is no prior art available at all which teaches the pre-heat treatment of natural gas or propane gas for the purpose of increasing its thermal efficiency in accordance with this invention.
Furthermore, it is presently believed in the gas combustion appliance industry that pre-combustion treatment of fuel, as contemplated in this invention, is not affective to increase thermal efficiency. In fact, a correction formula is always employed in the industry to eliminate any variance in fuel efficiency calculations due to a change in fuel supply temperature. Such correction formula calculation may be found in the "Gas Engineers Handbook", Ninth Printing, Chapter 8, "Gas Calorimetry", Pages 6-42.
Therefore, the method and device as disclosed in the present invention is completely contrary to industry norm, and is not at all obvious or known in the art.